Obtaining improved surface finishes on double reduced material



g 17, 1965 o. w. JAMES ETAL 3,200,629

OBTAINING IMPROVED SURFACE FINISHES 0N DOUBLE REDUCED MATERIAL Filed July 18, 1961 '2 Sheets-Sheet 1 M/VE/VTORS Owen W. James v Eqyene I Wafers A TTOR/VEY Aug- 1965 o. w. JAMES ETAL OBTAINING IMPROVED SURFACE FINISHES 0N DOUBLE REDUCED MATERIAL Owen W. James WU N mm n P 8 n M U E United States Patent 3,200,629 OBTAINING IMPRGVED SURFAQE FENISHES 0N DOUBLE REDUCED MATEREAL Owen W. .iames and Eugene P. Waters, both of Baitimore,

Md., assignors to Bethlehem Steel Qorporation, a corporation of Delaware Filed .tuiy 18, 1961, Ser. No. 124,385? 8 Claims. ((Jl. '72--21) The present invention relates to a method and means for producing very thin tin-coated ferrous sheet and strip material. More particularly the present invention relates to a novel method and means for providing a superior surface finish upon very thin tin-coated ferrous sheet and strip material.

Recently very thin tin-coated strip has been produced by rolling steel strip in conventional fashion, coating the strip with tin according to normal practice and then finally passing the coated strip through a second cold rolling operation which reduces the strip and its coating to a still lighter gauge. Although the tin coating is softer than the ferrous base, both the coating and the base metal are reduced approximately proportionally. Reduc tions may be made to almost any reasonable extent. However, the normal reduction is usually from 35 to 50% Thin coated strip material produced according to this method is known as double reduced material since it has been passed through two series of reducing operations.

While double reduction produces excellent thin tincoated strip material possessing very satisfactory ph' sical properties, trouble has been experienced with the surface finish due to roll marks, staining and particularly mottling of the surface.

Users of tin plate and strip, especially can manufacturers, are very demanding with respect to the surface finish of the product and particularly with respect to uniformity of finish. In addition, users of tin-coated prod ucts also desire various degrees of brightness of surface on the strip and sheet which they purchase.

. Heretofore the mottled and uneven surface finishes on double reduced material have been covered up by passing the double reduced material through a skin pass rolling stand between rolls which have been roughened by some expedient such as sand blasting. This operation breaks up the surface and results in a comparatively rough or coarse finish which more or less hides the underlying mottling. This solution of the problem is not satisfactory, however, because the mottling is not completely hidden, many purchasers of tin coated product do not desire a coarse finish, and the roughened skin pass rolling operation adds an extra step to the double reduction operation.

The cold rolling of metal produces considerable heat as a result of the work done in reducing the metal. This heat must be removed to prevent a progressive alteration in the size and shape of the roll pass due to gradual ex pansion of the rolls as the heat builds up. Conventional practice is to flood the rolls with cooling water to remove the heat. v Cold reduction by rolling is usually conducted with a lubricating or rolling oil to prevent sticking of the metal to the roll surface and to reduce the horizontal friction factor so that reduction is more easily accomplished. Modern practice has almost universally been to form an emulsion of the lubricating oil and cooling water and ap ply the emulsion to the strip entering the roll bite. It has been thought that the rolling oil and water emulsion acts as a unitary and homogeneous fluid medium for both cooling and lubricating the rolling operation.

The present inventors have discovered that it is free water in-the roll bite which causes the mottling of double reduced tin coated strip material. In particular they have found that the conventional oil and water emulsion tends to break down, especially when subjected to the heat and pressure of the roll bite. No practical method is known to prevent this breakdown as the stable emulsion point is very critical. The inventors have discovered, however, that if the reduction of the already coated strip is carried out in a uniform lubricating oil medium consisting only of oil or of Well mixed oil mediums which are thoroughly miscible with each other the mottled surfaces are eliminated. Furthermore, they have discovered that if the rolling is carried out with the correct lubricating conditions an even and uniform texture will be obtained regardless of changes in mill speed, roll temperatures and roll finishes, or surface conditions of material entering the mill. They have also discovered that a mixture of palm oil and alkyl esters of fatty acids forms a very superior rolling medium when a very bright strip surface is desired.

In order to cool the work rolls, the inventors apply cooling water to the rear of the work rolls and provide means to prevent the cooling water from reaching the entrance side of the work rolls where it could enter the roll bite. These means include the use of special splash shields in combination with a novel matching of the work surfaces of the work rolls and the back-up rolls.

It is an object of the present invention therefore to provide a method of rolling double reduced sheet and strip material with a uniform unmottled surface texture.

It is a further object of the present invention to provide rolling mill apparatus adapted to provide oil lubrication on the entrance side of the work rolls and Water cooling on the exit side of the work rolls and to prevent water from reaching the entrance side of the Work rolls. It is a still further object of the present invention to provide a method of rolling double reduced coated sheet and strip material having a uniform texture unmottled bright surface by rolling with a water-free lubricant comprising a glyceride of a fatty acid either alone or containing an alkyl ester of a fatty acid, while at the same time water cooling the rolls.

It is a still further object of the present invention to provide a Work roll and back-up roll combination which will prevent the migration of water films from the exit to the entrance side of the work rolls.

These and other objects and advantages will be recognized from an examination of the following drawings and description in which like numbers refer to the same structures and in which:

FIGURE 1 shows in section an elevation of a rolling mill arranged according to the present invention.

- FIGURE 2 shows a section in plan of FIGURE 1 along line 22 with top back-up roll and top water shield flaps removed.

FIGURE 3 illustrates the conformation of the surface of the work rolls and the arrangement of the work rolls and the back-up rolls.

FIGURE 4 shows in expanded view the ends of the work rolls and the back-up rolls of the present invention.

FIGURE 5 is an isometric view of the entry water shield.

A section of a roll stand 12 is shown in outline in FIG- URES 1 and 2. Back-up rolls 14 and 16 mounted in stand 12 are shown in section in FIGURE 1. Work rolls 18 and 20 are shown in section between back-up rolls 14 and 16. Tin coated strip 22 is fed from a coil of strip on feed reel 24 over guide roll 26, between work rolls 18 and 24), past guide rolls 28 and 29 to tension or takeup reel 30. A plurality of lubrication spray nozzles 32 and 34 spray a homogeneous mixture of a lubricating oil such as palm oil and an alkyl ester of a fatty acid onto the top and'bottom surface of strip 22. Sufficient oil mixture is sprayed onto both surfaces of the strip to fully cover the strip with a thin film of oil. At the roll bite some of the oil is squeezed from the surface so that the oil builds up at this point, particularly on the top surface of the strip, and the strip is consequently substantially completely flooded with lubrication oil.

Just to the left of sprays 32 and 34am entry water shields 36 and 38 each of which, as shown more clearly in FIGURE 5, Consists of a side plate 40, a bottom plate 42 and an inclined'top plate 44. Bottom plate 42 as may be clearly seen in FIGURE is formed from a relatively heavy metal section with a beveled end 4.3. Bevel 43 extends into or towards the roll bite as may be seen in FIG- URE l and the bevel prevents the edge of plate 42 from contacting the lower work rolls 2%. The side of plate 42 may also be beveled as seen in FIGURE 5 so as to eliminate a sharp edge along this side which might mar the bottom of strip 22 if it should touch plate 42. At the rear of the bottom plate 42 of both water shields 36 and 38 are secured clamp members 46 having arm members 47. As may be seen in FIGURES 1 and 2 entry water shields% and 3% may be placed in position on both sides of strip 22 by sliding the shields 3t; and 38 across cross member 48 of roll stand 12 until the arm members 47 of the clamps 4-6 engage the underside of member 4%. Screw clamps, not shown, may be passed through arm members 47 from the bottom if desired to engage cross member 48 to lock the two members 4b and 4-8 together more securely. During operation of the roll stand, shields 36 and 38, as shown in FIGURES 1 and 2, are positioned with their bottom plates under and very near but not touching the lower surface of the strip 22 passing to the bite of the work rolls while their side plates 40 are closely adjacent the sides of the strip and their inclined top plates 44 are located over but spaced considerably away from the strip surface. In order to facilitate drainage of any splashed water from shields 36 and 38, it is preferable that they be tipped rearwardly towards clamps 46 so that moisture will not drip from bevel 43 onto the lower work roll. Four water shield flaps 50, 52, 54 not shown, and 56 are pivoted on shafts 50a, 52a, 54a, not shown, and 56a supported by the mill stand structure 12 as shown in FIGURES 1 and 2. Water shield flaps 59, 52, 54 and 56 are arranged somewhat outwardly of the sides 40 of water shields 36 and 38 to more effectively shield the roll bite and the strip entering the roll bite from any splashed water. It will be noted that water shield flaps 50, 52, 54 and 56 are arcuately concave in two unequal sized arcs toward the mill rolls and are positioned adjacent the rolls in order to close the spaces between the reducing and back-up rolls.

Positioned on the exit side of work rolls l8 and are top water spray nozzles 53 and bottom water spray noz zles 60 which spray cooling water on the exit sides of work rolls 18 and 20 respectively. Top water sprays 58 are mounted upon a so-called water scoop 62 which comprises a trough-like structure extending along the rear of the work rolls having a water wiper 64 mounted upon its lower section to bear against the work surface of the Work roll 18. Water wiper 64- may be composed of some flexible material and is designed to provide a water seal against the'surface of roll 18 so that substantially no Water will pass from the area on top of wiper 64 to the area adjacent the bottom. j The cooling water discharged against the surface of roll 18 by spray nozzles 58 runs down the roll surface to wiper 64 which wipe the water from the surface and directs it into water scoop 62, which 64 out of the way when changing the rolls in stand 12. Bottom water spray nozzles of discharge their cooling water against the rear of bottom work roll 20 where both because of the effects of gravity and because work roll 20 is turning in the direction shown by the arrows in FIGURE 1; the water flows downwardly away from strip 22 and eventually into the sump, not shown, under the mill. A water scoop such as 62 is thus unnecessary to prevent the spray from bottom cooling nozzles 60 from contacting the strip 22.

A film of water from both groups of spray nozzles 53 and 6b is carried on work rolls 18 and 20 respectively, on the surface thereof to the areas of contact between the said work rolls and their respective back-up rolls 14 and 16. Because of the very high pressure'and close contact between the work rolls and back-up rolls water cannot pass between these rolls but 'is instead squeezed out and forced along the rolls to the sides thereof where it drains away. 'It is'important than the surfaces of' the back-up and work rolls be smooth and free from any imperfections or scuff marks which might allow water to pass between the rolls. 7

There is considerable agitation and violent splashing of water to the rear of the rolls but splash water shields as and 38 and water shield flaps 5t 52, 54 and 56 effectively shield strip 22 near the entrance side of rolls 18 and 2e, and also shield the work surface of the entrance side 7 of work rolls 18 and 20 themselves from any water which may be splashed or thrown from the exit side of the mill. Water shields 36 and 38 are mounted on clamps and water shield flaps 50, 52, 54- and 56 are pivotally mounted so that they can be removed or swung clear during the periodic changing of the rolls.

. While the back-up rolls 14 and 16 effectively squeeze the cooling water from the surface of the rotating work rolls and the various water shields described above effectively prevent any water droplets from splashing from the area contacted by the cooling water to the entering strip or the roll bite of the mill, it has been found that water may still work its way around from the exit side of the work rolls to the Work surface on the entrance side of the work rolls. The inventions prevent this by beveling the ends of'the back-up rolls and by cutting shoulders on the ends of the work rolls directly opposite the inner ends of the bevels on the back-up rolls. This structural relationship is shown in FIGURES 3 and 4 where the work surfaces 68 and 70 of work rolls l8 and 20 respectively have been cut back at 72 providing a sharp shoulder at 74 exactly opposite the edge 76 of the bevel surface 78 on back-up rolls 14 and 16. Work rolls 1% and 20 are beveled at 80. Cut 72 may initially be formed about one eighth of an inch deep so that as the rolls are subsequently reground the cut will remain at least one thirty-second of an inch deep. One thirty-second of an inch is approximately the minimum desirable. However the cut may be made deeper than one eighth inch initially if desired. It may be clearly seen in FIGURE 4 that the cut back surface 72 of work roll 18 is opposite the beveled surface '78 of back-up roll 14 with the edge '76 of bevel surface 78 of back-up rolls 14 exactly in line. with and meeting the edge of shoulder 74 between the work surface 68 and the cut back surface '72 of work roll 18. The exact dimensions of the bevels on both the back-up and the work rolls and the cut back portions on the work rolls are not critical. It will be understood, however, that shoulder 74 is preferably substantially a sharp shoulder and the edge of this shoulder and the bevel edge 76 must be substantially exactly in line with each other.

While the foregoing is the inventors preferred embodi merit and is particularly effective other configurations of rolls can be used, the most important consideration being that the working surfaces of the work rolls and back-up rolls be maintained of equal length and inexact alignment with each other.

It is particularly important in the cold rolling of coated materials to provide the correct rolling lubricant.

It has been found that excellent even textured so-called matte surfaces or dull surface finishes can be obtained by using a glyceride of a fatty acid as the lubricant on the entry side of the mill. By fatty acid it should be understood that the substances referred to are the fatty acids having suitable rolling lubrication properties, i.e. in general those fatty acids containing from 6 to 22 carbons. For example, pure palm oil or other comparable vegetable oil such as cottonseed oil or soybean oil constitute satisfactory lubricants. Other suitable fatty oils such as oils of animal or vegetable origin may also be used. If a brighter but also even textured surface finish is desired alkyl esters of fatty acids may be mixed with these rolling oils in various proportions depending upon how bright a surface is desired. Alkyl esters of fatty acids are completely miscible with these rolling oils so that a homogeneous lubricant is obtained. Any suitable commercial chemical proportioning equipment may be used to correctly mix and proportion the rolling and alkyl esters. The alkyl esters of fatty acids in effect cut the lubricating value of the rolling oil so that the frictional factor is increased.

This causes more burnishing and consequent brightening of the metal surface as the roll surfaces slip over the strip surface on both sides of the no-slip line, which is the point where the roll surface and the strip are traveling at exactly the same speed. It has been found that strip material having excellent surface characteristics and a very desirable degree of brightness can be obtained by the use of a rolling lubricant composed of 80 percent palm oil and 20 percent alkyl esters of fatty acids such as a proprietary product known as Petrosan. Petrosan is a methyl ester of various fatty acids, principally oleic, stearic and palmitic acids. Ethyl, amyl, and octyl esters of these or other fatty acids are equally suitable. More Petrosan can be used if brighter material is desired. We have, in fact tried rolling with 100% Petrosan and have obtained a successful operation and a satisfactory product, without excessively increasing the mill load. In addition to increasing the brightness of the strip, the use of Petrosan reduces the amount of power necessary to roll the strip, as compared with the power required when an oil-water emulsion is used. It has been found, for instance, that using the 20/80 Petrosan palm oil mixture, a strip may be rolled with approximately 26 horsepower per ton, while a comparable oil water emulsion would require more screwdown pressure and approximately 50 horsepower per ton to force the strip through the mill at the same speed and with the same reduction in strip thickness. Petrosan and Petrosan type substances are particularly suitable for a rolling oil additive since it has been found that they provide the desirable burnishing action without appreciably raising the mill load as would normally be expected.

A surprising result of rolling with water-free mixtures o f rolling oil and alkyl esters of fatty acids is that the surface of the rolled tin coated sheet will have essentially the same surface texture or finish regardless of wide variations in the rolling conditions such as roll temperature, speed of rolling, roll finishes and even surface finish of the material entering the mill, so long as a uniform composition and film of oils is interposed between the material being reduced and the rolls. This is an unexpected but very valuable advantage when it is considered that uniformity of surface is desired on a coil-to-coil, order to order, or day to day, basis regardless of changes in mill speeds, roll changes, changing roll temperatures, variations in required reductions, and variations in the appearance of coils entering the mill.

As an example for our invention, we start with a coil of tinplate produced in the usual manner on an electrolytic tinning line The tin coating on the tinplate is heavier than that desired in the final product, in order to allow for reduction of the tin coating in the final rolling operation.

The coil is placed on feed reel 24, and the end of the strip is threaded through work rolls 18 and 20, past rolls 28 and 29, and secured to take-up or tension reel 30. As the rolling operation is started, oile.g., palm oil, is sprayed onto the upper and lower sides of strip 22 by means of sprays 32 and 34 prior to its entry into the roll bite; On the rear or exit side of the rolls, cooling water is sprayed onto the work rolls by means of water sprays 58 and 60. The Work rolls and the tension on the strip are adjusted to effect a reduction of the strip gauge of 40%. plated strip having a moderately dull but uniform textured surface, suitable for the majority of uses to which thin tin plate can be put.

In producing strip on which a much brighter surface was desired, we followed the same procedure as given above except that instead of using palm oil alone as the lubricant we used a mixture of palm oil and 20% Petrosan.

It will be recognized that the ,present invention provides a very practical and-reliable method and means for obtaining even textured double reduced strip material in a single cold rolling stand without the use of any expensive or complicated special. equipment.

Although the present invention has been described herein in considerable detail, it should not be limited narrowly to the exact and specific particulars disclosed and/or described but may also include such substitutes, modifications or equivalents as are included within the scope and spirit of the invention or pointed out in the appended claims.

We claim:

1. A method of producing unmottled uniform texture surfaces on double reduced tin coated sheet and strip material comprising spraying a water-free mixture of palm oil and an alkyl ester of fatty acids on the material entering the reducing rolls, applying cooling water to the exit sides of the reducing rolls, shielding the material entering the roll bite and the entrance side of the reducing rolls from water splashed from the exit side of the rolls and preventing any water from migrating around the end of the reducing rolls from the exit to the entrance side, the alkyl ester, comprising a lower straight chain alkyl ester of fatty acid containing from 6 to 22 carbon atoms, serving to decrease the lubricity of the palm oil to increase the brightness of the product.

2. A method of reducing tin coated ferrous strip comprising passing said material through a cold rolling mill having a pair of work rolls, spraying a moisture free mixture of palm oil and a lower alkyl ester of a fatty acid upon the material entering the work rolls, spraying cooling water upon the rear of the work rolls, and preventing cooling water from reaching the entrance side of the roll bite, the alkyl ester reducing the lubricity of the palm oil to increase the brightness of the product without mottling.

3. A method of reducing tin coated ferrous strip comprising spraying a moisture free mixture of palm oil and a methyl ester of a fatty acid upon the material entering'the roll bite, spraying cooling water upon the rear of the work rolls, and preventing cooling water from reaching the entrance side of the roll bite to provide an even, unmottled surface finish on the reduced tin coated strip.

4. A method of reducing tin coated ferrous strip comprising spraying a moisture free mixture of vegetable oil and an organic compound completely mutually soluble with the vegetable oil upon the material entering the roll bite, said organic compound having a lower lubricity value than the vegetable oil, spraying cooling water upon the rear of the work rolls, and preventing any cooling water from reaching the entrance side of the roll bite to provide an even, unmottled surface finish on the reduced tin coated strip.

5. A method of reducing tin coated ferrous strip comprising spraying a moisture free mixture of palm oil The resultant product is a thin tin and a methyl ester of stearic acid upon the material entering the roll bite, spraying cooling Water upon the rear of the Work rolls, and preventing Water from reaching the entrance side of the roll bite to provide an even, unmottled surface finish on the reduced tin coated strip.

6. A'method of reducing tin coated ferrous strip comprising spraying a moisture free mixture of palm oil and methyl esters of stearic, oleic, and palmitic acids upon the material entering the roll bite, spraying cooling Water upon the rear of the Work rolls, and preventing free moisture from reaching the entrance side of the roll bite to provide an even, unmottled surface finish on the reduced tin coated strip.

'7. A-method of producing thin tin plate comprising applying a tin coating to a steel strip, rolling the strip in a cold rolling mill to an extent sufficient to substantially reduce the thickness of the strip While applying a water free roll lubricating oil to the strip on the entry side of the mill, applying cooling water to the rolls on the exit side of the mill, and preventing water from coming in contact with the strip on the entry side of the mill to provide an even, unmottled surface finish on the reduced tinplate.

8. A method of cold rolling tin coated strip material in a four-high mill comprising applying rolling oil to the entrance side or" the Work rolls and cooling Water to the exit side of the work rolls and preventing the cooling water from reaching the entrance side of the Work rolls by maintaining the working surfaces of the Work rolls and back-up rolls precisely equalin width and 0 w exactly in alignment to provide a uniform, unmottled surface finish on the cold rolled coated strip.

References Gated by the Examiner UNITED STATES PATENTS 7/23 Pelly 252-56 1,616,033 2/27 Gerlach 60.6 1,852,765 4/32 Wilson e 80-606 2,096,390 10/37 Burwell et a1. 252-56 2,107,541 2/38 Long 8041 2,157,455 5/39 Kimmel 80-38 2,181,173 11/39 Catulle S033 2,234,153 3/41 Herbert 801.2 2,275,113 3/42 Simburg 801.2 2,384,086 9/45 Glock 29-17 XR 2,849,905 9/58 Heinz 8041 2,896,486 7/59 Donnell 8060 2,914,975 12/59 Cavanaugh et al. 8060 FOREIGN PATENTS 297,201 9/28 Great Britain. 402,262 11/ 3 3' Great Britain.

OTHER REFERENCES Metals Handbook, 1948 Edition, published by the American Society for Metals, Cleveland, Ohio; pages 710 and 711.

CHARLES W. LANHAM, Primary Examiner.

LEON PEAR, MICHAEL V. BRINDISI, Examiners. 

1. A METHOD OF PRODUCING UNMOTTLED UNIFORM TEXTURE SURFACES ON DOUBLE REDUCED TIN COATED SHET AND STRIP MATERIAL COMPRISING SPRAYING A WATER-FREE MIXTURE OF PALM OIL AND AN ALKYL ESTER OF FATTY ACIDS ON THE MATERIAL ENTERING THE REDUCING ROLLS, APPLYING COOLING WATER TO THE EXIT SIDES OF THE REDUCING ROLLS, SHIELDING THE MATERIAL ENTERING THE ROLL BITE AND THE ENTRANCE SIDE OF THE REDUCING ROLLS FROM WATER SPLASHED FROM THE EXIT SIDE OF THE ROLLS AND PREVENTING ANY WATER FROM MIGRATING AROUND THE END OF THE REDUCING ROLLS FROM THE EXIT TO THE ENTRANCE SIDE, THE ALKYL ESTER, COMPRISING A LOWER STRAIGHT CHAIN ALKYL ESTER OF FATTY ACID CONTAINING FROM 6 TO 22 CARBON ATOMS, SERVING TO DECREASE THE LUBRICITY OF THE PALM OIL TO INCREASE THE BRIGHTNESS OF THE PRODUCT. 